Journal of Conference Abstracts

The Effect of Liming on the Availability of Phosphorus to Plants in Acid Forest Soils

A. Fransson (Ann-Mari.Fransson@planteco.lu.se) & B. Bergkvist (Bo.Bergkvist@planteco.lu.se)

Plant Ecology, Lund University, Sweden.

To study the effects of liming on the P available to plants in an acidic forest soil, homogeneous plots in Brönnestad, southern Sweden, were treated with lime: one with an easily soluble P fertiliser, and one with more insoluble fertiliser. Other plots were treated with combinations of the fertilisers and lime. Soil solution was collected during the next two years and the bulk soil was sampled after two years. The soil was extracted with oxalate/oxalic acid and analysed by ICP-AES. Oxalate/oxalic acid was chosen as extractant of the plant available phosphorus because anion-chromatography revealed that oxalate is present in the soil solution and among the organic acids produced by plants, oxalic acid is the one of the most effective in solubilising P. Apart from oxalic acid, acetic, lactic and formic acid were found in the soil solution.

Phosphorus concentrations in the extracts from all horizons were strongly correlated with the Al concentration in the extract, suggesting that the P extracted was associated with Al in the soil. In the E and B horizons, the P concentration also was strongly correlated to the Fe concentration of the extract. This correlation was not found in the humus, suggesting that the extractable P in the humus could come from organically associated Al-phosphates. The amount of P extracted from the O and E horizons did not differ. However, in the B-horizon the amount of P extracted was greater even at the same oxalate concentration and the total amount extractable was more than double that from the E horizon.

Liming decreased the positive effects of P fertilisation in an acid forest soil by reducing the concentration of P in the soil solution. Less P could be extracted with oxalate/oxalic acid if the soil was limed compared to a non limed treatment. The P concentration from the limed treatments did not differ from the non treated soil. More results will be presented on the poster.

Nitrogen Leaching from Peatlands

Shimna M. Gammack¹ (s.m.gammack@abdn.ac.uk), L. Yesmin² (lyesmin@cc.UManitoba.CA) & Malcolm S. Cresser¹ (m.s.cresser@abdn.ac.uk)

¹ Department of Plant and Soil Science, University of Aberdeen, Aberdeen AB24 3UU, Scotland, U.K.

² Current address: University of Manitoba Natural Resources Institute, Manitoba, R3T 2N2, Canada.

Greenhouse experiments in which intact peat turfs were subjected to artificial rain formulations with varying loads of N deposition and different ratios of ammonium-N to nitrate-N have shown that the distribution of N species in the leachate is determined by N inputs in simulated rainfall. Total nitrogen leaching increased with total nitrogen input. Total nitrogen leaching increased with increasing nitric acid in the artificial rain, with the increase in total N output being largely due to increased nitrate output, and increased to a lesser extent with increasing ammonium sulphate deposition.

Vegetation type had an effect on nitrogen leaching, with much greater leaching from Calluna-dominated peat turfs than from grass-dominated turfs.

Soil pH decreased with increasing nitric acid deposition, and decreased to a lesser extent with increasing ammonium sulphate deposition.